Craniofacial surgery is guided by 3D images reconstructed from CT or MR scans, but the validity of these graphically rendered images has not been tested under controlled circumstances. We simulated craniofacial surgical procedures and tested each step in the process used to create and apply the images against an independent standard for truth. The ability to measure 3D bony objects in these image volumes was tested for accuracy and repeatability. Surgery was simulated and performed on cadavers and the results compared with direct measurements. Surgical correction of craniofacial abnormalities in three pediatric patients was tested for the validity of the simulations. We found that the 3D spatial measurement accuracy of 3D image volumes obtained from CT scans was high, allowing surface landmark identification within 1 voxel, physical change detection within 1 mm and 2 degrees, and matching of surfaces within 1 degree and 1 voxel under ideal conditions. The error increased to 4 mm and 3 degrees on the average in cadaver and patient simulations. 3D CT reconstructions provide acceptable bony structural detail for planning and describing craniofacial surgical interventions, and surgical simulation images accurately depict post-operative outcome.